Internalization, phagolysosomal biogenesis and killing of mycobacteria in enucleated epithelial cells

Area of Science:

• Cell Biology
• Microbiology
• Immunology

Background:

• Intracellular pathogens can trigger host cell transcriptional responses.
• The necessity of the host cell nucleus for intracellular bacterial infection development is often unknown.
• Enucleated host cells (cytoplasts) are a model to study nuclear requirement, primarily used for viral infections.

Purpose of the Study:

• To investigate the role of the host cell nucleus in Mycobacterium smegmatis infection.
• To examine M. smegmatis internalization, phagosome biogenesis, and survival in enucleated lung epithelial cells.

Main Methods:

• Infection of enucleated (cytoplasts) and nucleated type II alveolar epithelial cells with M. smegmatis.
• Scanning electron microscopy to visualize bacterial internalization.
• Analysis of phagosome-lysosome fusion and mycobacterial killing efficiency.

Main Results:

• M. smegmatis infection percentage was lower in cytoplasts than nucleated cells.
• Bacteria were internalized via a phagocytosis-like mechanism in both cell types.
• Phagosome-lysosome fusion and M. smegmatis killing were more efficient in enucleated cells.
• Enucleated cells showed increased autophagic vesicles, potentially linked to enhanced killing.

Conclusions:

• The host cell nucleus is not required for the full development of M. smegmatis infection.
• Mycobacterial killing and phagosome maturation processes can occur efficiently in the absence of the nucleus.
• Host cell nucleus absence may enhance autophagic processes contributing to pathogen clearance.